INFRARED DIODE-LASER SPECTROSCOPY OF THE ALLYL RADICAL - THE NU-11 BAND

Allyl radicals were generated by the photolysis of 1,5-hexadiene at 193 nm and were detected by observing the nu-11, i.e., CH2 symmetric wagging band by infrared diode laser kinetic spectroscopy. The observed spectrum showed clearly the effect of nuclear-spin statistical weights, establishing the presence of a C2b axis in the molecule The spin-rotation splitting was not resolved; only some high-K(a) lines were found broader than others, placing an upper limit for the epsilon(aa) constant at about 200 MHz or less. The rotational constants derived from the observed spectrum indicate that the molecule is essentially planar. The C-C bond length and the CCC bond angle were calculated from the ground-state rotational constants to be 1.3869 angstrom and 123.96-degrees, respectively, where structural parameters involving hydrogens were fixed to those of ab initio values.